In a manufacturing process of a semiconductor device or the like, a surface of a semiconductor wafer (hereinafter referred to as “wafer”) is subjected to a process with the use of a process liquid, such as an etching process and a polymer removal process, and then the surface is subjected to a drying process (see, JP6-9130U, for example).
As an example of processing a wafer with a process liquid, an etching process is described below.
Specifically, an etching liquid such as a hydrofluoric acid solution (HF liquid) is supplied onto a surface of a wafer placed in a chamber of a substrate processing apparatus to conduct an etching process such as a dilute hydrofluoric cleaning and a buffered hydrofluoric acid cleaning, and then a rinse liquid such as a deionized water is supplied onto the surface of the wafer to clean the same. As an etching liquid, there may used a liquid other than the hydrofluoric acid solution (HF liquid), namely, a liquid containing ammonium fluoride, for example. Thereafter, the wafer is dried.
The etching liquid used in the etching process is discharged from the chamber, and is collected to be reused. Namely, the etching liquid discharged from the chamber is returned to an etching-liquid supplying part for supplying an etching liquid onto a surface of a wafer, and the etching liquid is again supplied onto a surface of a wafer.
As a method for drying a wafer, there has been conventionally known a steam drying method in which a vapor of an organic solvent such as isopropyl alcohol (IPA) is supplied onto a surface of a wafer which is being rotated. It has been proposed, in order to prevent generation of watermarks on a surface of a wafer during the drying step, to supply a dehumidified air into a chamber so as to lower a humidity around the wafer.